[z0rimo]

Fixes #33733

This adds a dedicated ClrTypeChangeExpression which allows a SQL expression to expose a different CLR type without emitting a corresponding SQL conversion.

• Add a CLR type change SQL expression which is omitted during SQL generation.
• Integrate the expression with type mapping, nullability processing, SQL generation, and parentheses handling.
• Use it for enums configured with EnumToStringConverter<>, avoiding unnecessary SQL CASTs for ToString().
• Extend the existing string-converted enum regression coverage with a composed ToString().Contains(...) case.

Local validation:

• ./build.sh
• EFCore.ApiBaseline.Tests: 14 passed
• EFCore.Relational.Tests: 1,525 passed, 1 skipped
• EFCore.Sqlite.FunctionalTests: 38,334 passed, 285 skipped
• Focused string-converted enum tests passed

SQL Server functional tests were not executed locally because the project skips tests on non-Windows environments when Test__SqlServer__DefaultConnection is not configured. The SQL Server test project and updated SQL baselines build successfully.

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• The code builds and tests pass locally (also verified by our automated build checks)
• Commit messages follow this format:

        Summary of the changes
        - Detail 1
        - Detail 2

        Fixes #bugnumber

• Tests for the changes have been added (for bug fixes / features)
• Code follows the same patterns and style as existing code in this repo

[Copilot]

🟡 Changes recommended

Removing casts exposes SQL Server store-type mismatches and truncation regressions in composed string operations.

2 open issues

• Preserve varchar mapping for enum STRING_AGG separators · New
• Restore nvarchar(max) widening for enum Replace results · New

What changed in this PR

Adds a SQL expression that changes the exposed CLR type without emitting a SQL conversion, addressing #33733 for string-converted enums.

Changes:

• Introduces ClrTypeChangeExpression and integrates mapping, nullability, SQL generation, and parentheses handling.
• Uses the new expression for enum ToString() translation.
• Updates API baselines and adds composed ToString().Contains(...) coverage.

File	Description
test/​EFCore.SqlServer.FunctionalTests/​Query/​AdHocMiscellaneousQuerySqlServerTest.cs	Updates SQL Server baselines and adds the composed query baseline.
test/​EFCore.Sqlite.FunctionalTests/​Query/​AdHocMiscellaneousQuerySqliteTest.cs	Updates SQLite baselines and adds the composed query baseline.
test/​EFCore.Relational.Specification.Tests/​Query/​AdHocMiscellaneousQueryRelationalTestBase.cs	Adds shared result assertions for composed string operations.
src/​EFCore.Relational/​Query/​SqlNullabilityProcessor.cs	Propagates operand nullability through the new expression.
src/​EFCore.Relational/​Query/​SqlExpressions/​ClrTypeChangeExpression.cs	Defines the CLR-only type-change expression.
src/​EFCore.Relational/​Query/​SqlExpressionFactory.cs	Supports mapping the new expression.
src/​EFCore.Relational/​Query/​QuerySqlGenerator.cs	Emits only the operand and handles parentheses.
src/​EFCore.Relational/​Query/​Internal/​Translators/​EnumMethodTranslator.cs	Replaces string-converted enum casts with the new expression.
src/​EFCore.Relational/​EFCore.Relational.baseline.json	Records the added public and protected APIs.

_{Review effort: Balanced}

[Copilot]

🟡 Changes recommended

The PR bundles an unrelated SQL Server REPLACE translation change, which widens bounded varchar inputs to varchar(max) and affects plain string columns, but the PR description covers only the enum CLR type change and the related tests are not yet explained or split out.

1 open issue

• Document or separate the unrelated SQL Server REPLACE widening change · New

2 resolved since last review

• Restore nvarchar(max) widening for enum Replace results
• Preserve varchar mapping for enum STRING_AGG separators

_{Review effort: Lite}

[Copilot]

🔵 Needs a closer look

Human verification is warranted because the change introduces a public SQL-expression node and cross-provider SQL generation changes that could affect SQL Server CAST behavior and downstream visitors, while SQL Server execution was unavailable locally.

No open issues 🎉

1 resolved since last review

• Document or separate the unrelated SQL Server REPLACE widening change

_{Review effort: Lite}

[AndriySvyryd]

Thanks for your contribution!

[github-actions]

API review baseline changes for src/EFCore.Relational/EFCore.Relational.baseline.json

Show diff

The diff below was generated by ApiChief between the base and the PR.

  class Microsoft.EntityFrameworkCore.Query.QuerySqlGenerator : System.Linq.Expressions.ExpressionVisitor
+ virtual Expression VisitClrTypeChange(ClrTypeChangeExpression clrTypeChangeExpression);

+ class Microsoft.EntityFrameworkCore.Query.SqlExpressions.ClrTypeChangeExpression : Microsoft.EntityFrameworkCore.Query.SqlExpressions.SqlExpression
+ virtual SqlExpression Operand { get; }
+ virtual ClrTypeChangeExpression ApplyTypeMapping(RelationalTypeMapping? typeMapping);
+ ClrTypeChangeExpression(SqlExpression operand, Type type, RelationalTypeMapping? typeMapping);
+ virtual ClrTypeChangeExpression Update(SqlExpression operand);

  class Microsoft.EntityFrameworkCore.Query.SqlNullabilityProcessor : System.Linq.Expressions.ExpressionVisitor
+ virtual SqlExpression VisitClrTypeChange(ClrTypeChangeExpression clrTypeChangeExpression, bool allowOptimizedExpansion, out bool nullable);